A drive pulley elevator with an elevator car, a counterweight and a drive unit installed below the travel path of the counterweight is known from U.S. Pat. No. 5,469,937, in which the drive unit is so constructed and arranged that it substantially does not project beyond the side surfaces, which are parallel to the shaft wall at the counterweight side, of the counterweight. It is thus achieved that the elevator car, measured at right angles to the shaft wall at the counterweight side, can have a largest possible width and in that case can move past the drive unit without an installation space for the drive unit outside the shaft cross-section being necessary.
An elevator installation constructed in accordance with the teaching according to U.S. Pat. No. 5,469,937 has the disadvantage that the runs, which extend from the drive pulley of the drive unit to deflecting pulleys present in the shaft head, of the elevator support means have to be led laterally past the counterweight. The outer diameter of the drive pulley therefore has to be greater than the width of the counterweight measured parallel to the shaft wall at the counterweight side. Since a greater drive pulley diameter requires a greater torque of the drive motor and thus also larger motor dimensions, relatively tight limits are imposed on the drive pulley diameter and thus the mentioned width of the counterweight. The length of the counterweight in modern elevator installations is similarly strongly limited by the smallest possible shaft head heights and shaft pit depths, since the travel path length available for the counterweight is reduced by the drive unit mounted below the counterweight. The required mass of the counterweight can thus only still be achieved by increase in the thickness—measured at right angles to the shaft wall at the counterweight side—of the counterweight. Since modern elevator drives, thanks to highly flexible support means, work with very small drive pulley diameters and thereby with extremely small motor dimensions, the thickness of the counterweight in the case of the conditions described in the foregoing usually exceeds the size of the drive unit measured in the direction of this thickness, so that an optimum width, which corresponds with the given shaft cross-section and the given size of the drive unit, of the elevator car cannot be realized.